The United States pairing of Serena Williams and John Isner snuck into the Hopman Cup final with a 3-0 win over the Czech Republic at the Perth Arena on Thursday.
The pre-tournament favourites had to complete a clean sweep of the Czech combination of Lucie Safarova and Adam Pavlasek in the Group A tie to reach Saturday's final of the mixed teams tournament.
Having won both singles matches, Williams and Isner powered on through, taking the mixed doubles in straight sets, 6-3, 6-3.
But the Czechs came agonisingly close to making it to the final during the women's singles encounter that opened the tie.
Safarova, ranked 15th in the world, recovered from a set down against Williams in the game of the tournament, serving for the match at 6-5 in the third set.
However, the world number one was able to break back and eventually prevailed in a tense third-set tiebreaker 6-3, 6-7 (1/7), 7-6 (8-6) to keep the Americans in the hunt.
Isner then beat the 239th-ranked Pavlasek in straight sets, 7-6 (7/4), 6-4, to set up the mixed doubles decider.
The United States have claimed a record six Hopman Cup titles and both Williams and Isner have won in Perth.
Williams teamed with James Blake in 2003 and Mardy Fish in 2008 and can become the first three-time winner of the event, while Isner won with Bethanie Mattek-Sands in 2011.
Their opponents will not be known until after Friday's final round robin ties in Group B.
'Backs against the wall'
Williams was thrilled they were able to rise to the challenge. "We're really happy, we're really excited," she said. "Our backs were against the wall and I think that is when John and I play our best, when we are under pressure."
Williams said she was a little disappointed with her own form in the singles match against Safarova.
"I would love to do a little better, I missed a few shots and I was not aggressive," she said.
"Lucie played really well -- she was really aggressive, she kept hitting a lot of winners."
Earlier, Canada bowed out of contention despite a 2-1 win over Italy.
Like the Americans, the Canadian team of Eugenie Bouchard and Vasek Posposil needed to complete a clean sweep of the Italian pairing of Flavia Pennetta and Fabio Fognini in the Group A tie.
Bouchard and Posposil gave themselves a chance by winning both singles matches in straight sets, but then succumbed to the Italians in a tight mixed doubles rubber.
The doubles was decided by a match tiebreak, with the Italians winning their first rubber of the tournament, 6-3, 4-6, 10-7.
Bouchard got the Canadians off to a perfect start against the Italians with her second successive singles win of the tournament.
Having thrashed world number one Serena Williams on Tuesday, the 20-year-old starlet was too good for the 12th-ranked Pennetta, winning 6-3, 6-4.
Pospisil also kept his perfect record in singles this week, beating Fognini -- who did not take a match alone all week as he struggled with the Perth head -- in easy fashion, 6-0, 6-3.
However, the Canadian was unable to continue his form into the doubles, and he struggled against the Italians.